Calculation of Combustion Phases in a Diesel Engine Based on the Difference between Motoring and Combustion Pressures

Abstract

To analyze the combustion and exhaust characteristics of internal combustion engines, it is important to analyze combustion phases, such as ignition delay, premixed combustion period, and diffusion combustion period, by defining the start and end of combustion. This paper proposes a method for detecting and calculating combustion phases based on the difference between combustion and motoring pressures. The time at which 10% of the maximum pressure difference is observed can be considered as ignition timing, while that at 95%–99% as the end timing of combustion. Ignition delay and combustion duration calculated using the proposed method were almost identical to those calculated based on cumulative heat release. In addition, both methods exhibited a similar tendency with respect to the injection timing. A comparison of the results obtained via the two detection methods demonstrates that the error in the ignition delay was found to be considerably small, while that in the combustion duration reached 0.57°. Furthermore, a comparison of the proposed method and the complicated conventional method for detecting combustion phases based on cumulative heat release confirmed that the combustion phase can be detected via a simple calculation using the difference between the combustion and motoring pressures.